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05-05-2008, 01:47 PM   #1
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highlight recovery

I have a few blown pictures and did manage to recover detail in raw processing this did mean the overal image was darker though, if I can reover detail why does it blow out anyhow ? I mean its like the image sensor has another stop of infomation that is hardly ever used or am I imagining things ? I did get some swan detail back and a sky too (though it looks slightly unatural) I think also photoshops raw converter does some trhinking for itself in blown out bits and tries to aproximate what it thought there was supposed to be there

05-05-2008, 01:58 PM   #2
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mostly, it is based on the fact that "not all three channels bllow at once", which means that, if you are not very picky about color information, you can get some more detail in there. usually, when you have it bllown out, you are happy enough to have some detail in there to save the day and not much added color info, so it works . this is afaik, if somebody knows more, maybe he can explain.
05-05-2008, 02:04 PM   #3
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You're not imagining anything! There actually is quite a bit more information in a RAW image file than could be displayed on the screen, and therefor print. RAW files actually have detail in both directions, shadow and highlight that gets "clipped" so we can have a standard viewable image. Before I go on, I should mention that if you've got the dough, there are special monitors that can display a much higher dynamic range than our standards these days, they are VERY expensive, and benefit to us is minimal especially considering cost.

You might have heard all sorts of hullabaloo about something called "HDR". This is the current answer to the problem of limited dynamic range wherein the extra detail from a raw file, or more commonly several exposures can be "merged" into an image to show detail that normally would have been clipped in shadow or blown-highlights.

All this in mind, I generally try to underexpose my RAW shots by a slight amount, because I value highlight detail over shadow (I hate blown-out shots). I can then go into post processing, and do my own "clipping", much like you did to get at the detail you thought was gone.

This is the main reason why we should always shoot important things in RAW!

I hope that helps a bit, I'm happy to respond if I wasn't clear enough!
05-05-2008, 02:04 PM   #4
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As "nanok" said; your salvage results in an unnatural look because it lacks color data from at least one channel. There is no unused data, just partially (or, totally) missing data. You just cannot recover anything if all the color color channels are off.
Various software tools are available to "estimate" the possible color from a "blown" single channel; they may occasionally be useful. However; they do not "recover" data, they just add something that seems plausible according to their algorythms.


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